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Re: transformer theory q



Original poster: "Ed Phillips by way of Terry Fritz <twftesla-at-qwest-dot-net>" <evp-at-pacbell-dot-net>

Tesla list wrote:
> 
> Original poster: "Peter Lawrence by way of Terry Fritz
<twftesla-at-qwest-dot-net>" <Peter.Lawrence-at-Sun-dot-com>
> 
> Many thanks for all the responses so far to the transformer theory question.
> I think the answer to question 1 can be summarized as:
> 
>         fewer turns in the primary lowers its inductance and causes the
>         primary current to increase (at least when the secondary is unloaded,
>         not so sure about the loaded case). the effect is rather large,
>         a 10% decrease in primary turns can cause 5x primary current in the
>         unloaded condition.

	If you have too few turns the core can saturate and the currents will
be limited only by the primary resistance, the fuses or breakers on the
power line, and your tolerance to the smoke which is sure to come out.

> 
> I still have not heard a clear answer to part 2, what happens (to the primary
> current) when there are more than the recommended primary turns (take +10%
> as an example).

	Nothing much.  The core will run at lower flux density, the losses will
decrease, and the primary resistance and the leakage inductance will
increase a bit.  Far, far safer way to go!
 
> I am thinking of trying many taps on a test primary and finding the one that
> minimizes the primary current (in the unloaded secondary condition), does
this
> make sense? If I do this what happens when I put the shunts back in (or some
> fraction of the shunts), or should I do the experiment with the shunts?
> 
> thanks,
> Peter Lawrence.

	Share your results with us.

Ed